Clean up SearchableSnapshotActionIT

[nielsbauman]

As a follow-up of #133954, this class could use a clean up in deduplicating code, replacing some assertBusys with awaitIndexExists, and more.

[Copilot]

Pull Request Overview

This PR refactors the SearchableSnapshotActionIT test class to reduce code duplication, improve maintainability, and replace repetitive assertBusy calls with more specific helper methods.

• Replaces manual index existence checks and assertBusy with awaitIndexExists and awaitIndexDoesNotExist
• Consolidates duplicate snapshot retrieval logic into a reusable getSnapshots() method
• Replaces custom step key checking with TimeSeriesRestDriver.awaitStepKey()

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
SearchableSnapshotActionIT.java	Removes duplicate code patterns, replaces assertBusy with helper methods, removes unused imports and suppressions
TimeSeriesRestDriver.java	Adds awaitStepKey method and makes getStepKey public to support refactoring

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[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[dakrone]

LGTM, though I notice we're changing a lot of timeouts to be shorter. Do you have any concerns with that, or do we think things have sped up to where they shouldn't cause failures?

[dakrone]

We're switching these here from a 60 second timeout to a 10 second timeout, do you have any concerns about this failing in some cases?

[nielsbauman]

From what I could tell by looking at the history of this class, most timeouts looked like they were simply copied over from other places. And these 60-second timeouts are simply excessive; there is no way ILM needs a whole minute to get to that stage. I decided to clear out all custom timeouts to have a clean slate. I've been running this class on repeat for more than a day on 3 VMs. While that doesn't prove that no failures will occur on our CI VMs, I feel confident to merge this PR as-is. If failures do come up, I will take it upon myself to have a look at them. Although I'd probably first look at changing the setup/order of the test before resorting to simply increasing timeouts.